Bonded non-woven fibrous products and methods of producing them



3,012,911 BONDED NON-WGVEN FEBROUS PRGDUCTS AND METHODS OF PRODUCENG THEM Vincent J. Moser, Willow Grove, Pa, assignor to Robin & Haas Company, Philadelphia, Pa, a corporation of Delaware N Drawing. Filed May 13, 1959, Ser. No. 812,802 7 Claims. (6!. 117-l40) The present invention is concerned with the production of bonded non-woven products and particularly with prodnets of this type adapted to textile usage, for example in a garment or as part of a garment.

It has heretofore been suggested to employ addition polymers containing small proportions of acrylamide or methacrylamide in conjunction with thermosetting condensates of aminoplast or epoxy type for the purpose of bonding the fibers in non-Woven fabrics. The employment of the condensate in addition to the amide polymer was necessary to order to provide resistance to washing and dry-cleanin" since the application of the amide-containing polymer to the non-woven fibrous webs even when subjected to high temperatures such as 300 F., could not provide resistance to both washing and drycleaning in the resulting bonded fabric.

It is an object of the present invention to provide a modified amide-containing linear addition copolymer which is capable of being applied as a binder for the fibers of non-woven fabrics and yielding products, after curing, which have suflicient resistance to washing and dry-cleaning by chlorinated hydrocarbons for most practical purposes even without the employment of a thermosetting condensate such as an aminoplast or polyepoxide in conjunction with the amide-containing polymer. Other objects and advantages of the invention will be apparent from the description thereof hereinafter.

in accordance with the present invention, it has been discovered that certain linear addition copolymers containing amide groups and vinyl alcohol groups in certain proportions, when applied to non-woven fabrics and cured by heating at elevated temperatures, impart resistance to normal laundering operations such as may be performed with modern detergents of the type represented by Tide, All, and Fab, as well as resistance to dry-cleaning by chlorinated hydrocarbons such as carbon tetrachloride.

The linear addition copolymers of the present invention are those formed of units consisting essentially of about 4 to 6% by weight of methacrylamide, about to by weight of vinyl alcohol units, preferably about 8 to 10% of such vinyl alcohol units, about 1 to 45% by weight of a vinyl ester such as vinyl acetate, and about 46 to 90% by weight of units obtained from acrylic esters t of the formula:

where n is an integer having a value of l to 2, and R is an alkyl group having 4 to 18 carbon atoms. Examples of compounds of Formula I include butyl acrylate, butyl methacrylate, Z-ethylhexyl acrylate and methacrylate, noctyl acrylate or methacrylate, dodecyl acrylate, hexadecyl acrylate and octadecyl acrylate.

It has been found that the methacrylamide cannot be replaced entirely by acrylamide. The polymers obtained with acrylamide do not provide the resistance to Washing and dry-cleaning obtained by the methacrylamide copolymers.

The monomers from which the polymers are prepared are so selected as to yield a copolymer having an apparent second order transition temperature, herein designated T which is not over 20 C. The T value referred to herein is the transition temperature or inflection temperature which is found by plotting the modulus of rigidity against temperature. A convenient method for determining modulus of rigidity and transition temperature is described by I. Williamson, British Plastics 23, 87-90, 102 (September 1950). The T value hereused is that determined at 300 kg./cm

The linear addition copolymers are obtained by first preparing a copolymer of about 4 to 6% by weight of methacrylamide with about 7 to 50% by weight of a vinyl ester such as vinyl acetate, and about 46 to by weight of at least one ester of FormulaI above. These copolymers may be produced by conventional emulsion polymerization procedures employing a suitable emulsifier such as a non-ionic or an anionic emulsifier or mixtures thereof in conjunction with a free-radical initiator which may, if desired, be a component of any of the well-known redox systems. Examples of emulsifiers that may be used include sodium lauryl sulfate and t-octylphenoxypolyethoxyethanols containing from about 10 to 50 oxyethylene units per molecule. The amount of emulsifier may range from about /2 to 6% on the weight of monomers. Any free-radical initiator such as azodiisobutyronitrile, t-butyl hydroperoxide, and ammonium or potassium persulfates may be employed. The proportion of initiator may be from 0.1% to 2% on the weight of monomers.

The polymers used as binders of the present invention may also be graft or block copolymers wherein one or more, but not all, of the monomers are first polymerized and then one or more other monomers are copolymerized with the first polymer obtained. Thus, methacrylamide may first be homopolymerized or copolymerized with one or more, but less than all, of the 'comonomers to be introduced into the ultimate copolymer, and then the last monomer or monomers are added to the system and copolymerized or grafted on to the first homopolymer or copolymer formed. The same procedure may be used in reverse order to graft the rnethacrylamide on to a previously-formed homopolymer or copolyrner of other monomeric units. Again, a plurality of monomeric units may be introduced in succession and the methacrylamide may be introduced at the beginning, at any intermediate stage, or at the end as desired.

After preparing the linear addition polymer by emulsion polymerization which can generally be adjusted to provide a product containing anywhere from 20 to 60% solids, the copolymer is subjected to an agent for hydrolyzing the vinyl ester partially to introduce the required proportion of vinyl alcohol units into the desired polymer. This hydrolysis may be effected either on the acid or alkaline side, but preferably alkaline conditions are employed. To accomplish the hydrolysis, it is merely necessary to introduce an amount of alkaline material such as sodium hydroxide which is stoichiometrically equivalent to the proportion of vinyl ester units to be converted to vinyl alcohol units. After introduction of the alkaline material, the polymer dispersion is heated to a temperature of about to 200 F. for sufiicient time to useup the alkaline material which is readily determinable by testing the pH of the system periodically. The time varies inversely with the temperature and, of course, depends upon the proportion of vinyl alcohol units desired. Times of 15 to about 200 minutes or more may be employed for small batches.

After hydrolysis in this manner to introduce the desired proportion of vinyl alcohol units, the polymer dispersion may be diluted with water to provide the concentration at which it is to be applied which may be anywhere in the range from 5% to about 60% by weight of solids.

The term consisting essentially of as used in the definition of the components present in the copolymer claimed is intended to exclude the presence of other com- Patented Dec. 12., 1961 I the properties and characteristics possessed by the copolymer as set forth above, but to permit the presence of other components in such amounts as not substantially to affect said properties and characteristics adversely.

The eopolymer may comprise small amounts of other monomers such as styrene, vinyltoluene, vinyl chloride, acrylonitrile, or methacrylonitrile.

The fibrous webs may be formed in any suitable manner such as by carding, garnetting, or by dry deposition from an air suspension of the fibers. The expression random array when used hereinafter and in the claims is intended to include the array of fibers in a carded web or garnetted web wherein partial orientation is frequently present as well as other arrays in which the fibers are in a completely haphazard distributional relationship.

The fibers from which the webs may be made include cellulosic fibers such as cotton, rayon, jute, ramie, and linen; also cellulose esters such as cellulose acetate; silk, Wool, casein, and other proteinaceous fibers; polyesters such as poly(ethylene glycol terephthalate); polyamides such as nylon; vinyl resin fibers such as the copolymer of vinyl chloride and vinyl acetate, polymers of acrylo nitrile containing 70 to 95% by weight of acrylonitrile including those available under the trademarks Orlon and Acrilan; siliceous fibers such as glass and mineral wools.

The aqueous dispersion of the water-insoluble copolymer of the present invention may be applied to the web or mat of fibers in any suitable fashion such as by spraying, dipping, roll-transfer, or the like. An acid catalyst may be included in the aqueous dispersion at the time it is applied to the fibrous web or it may be applied to the fibrous web before or after the copolymer is applied. Examples of acidic catalysts that may be employed include oxalic acid, dichloroacetic acid, para-toluenesulfonic acid, and acidic salts such as ammonium sulfate and amine salts, such as the hydrochloride of 2-methyl-2- aminopropanol-l The proportion of the polymer that is applied to the web or mat is such as to provide 15 to 50% by weight of copolymer based on the total weight of copolyrner and fibers. After application of the aqueous dispersion of the water-insoluble copolymer to the fibrous web, the impregnated or saturated web is dried either at room temperature or at elevated temperatures. The web is subjected, either after completion of the drying or as the final portion of the drying stage itself, to a baking or curing operation which may be effected at a temperature of about 210 to 750 F. for periods which may range from about one-half hour at the lower temperature to as low as five seconds at the upper temperature. The conditions of baking and curing are controlled so that no appreciable deterioration or degradation of the fibers or copolymer occurs. Preferably, the curing is efliected at a temperature of 260 to 325 F. for a period of 2 to minutes.

It is believed that the curing operation in some way causes reaction of the polymer molecules to effect crosslinking thereof to a condition in which the binder is highly resistant to laundering and dry-cleaning. It is also believed that the curing causes some reaction between the polymer molecules and reactive groups in the fibers such as the hydroxyl groups of the cellulose fibers. While the precise nature of the reaction and the products thereby obtained are not clearly understood, it is presumed that the resistance to laundering and dry-cleaning is the result of the reaction between binder polymer molecules to cross-link them and/or the reaction between the binder polymer molecules and reactive sites of the fiber molecules. However, it is not intended to limit the invention by any theory of action herein stated.

The bonded fibrous products of the present invention are characterized by softness, flexibility, resistance to discoloration on exposure to ultraviolet light, resistance to chlorinated hydrocarbon dry-cleaning fluids, and resistance to laundering. Because of the softness and flexibility and good draping qualities of the products of the present invention, they are particularly well adapted for use in garments where porosity, especially to moisture vapor, and soft hand and feel, make the products advantageous where contact with the skin of a wearer may be involved. In general, the products are quite stable dimensionally and have good resilience and shape-retention properties. They are adapted for use not only in garments but as padding or cushioning, and moisture-absorbing articles, such as bibs and diapers. They are also useful as heatand sound-insulating materials and as filtration media, both for liquids and gases.

As stated hereinabove, the products obtained from non-woven fibrous webs employing the aqueous dispersion of the amide-containing and vinyl alcoholcontaining copolymers of the present invention impart good resistance to laundering and dry-cleaning when applied as the sole binder and cured in the manner stated hereinabove. Such products are also free of any tendency to become discolored on chlorination and ironing. However, for some purposes, particularly where chlorination and/or ironing are not encountered, the copolymer of the present invention may be employed in conjunction with a thermosetting resin condensate such as an aminoplast or polyepoxide. The amount of such condensate that may be included in the binder compositions may be as high as 20% by weight of the copolymer, a proportion of 3 to 10% being preferred when such condensate is used.

The aminoplast condensates which may be employed are the low molecular weight or monomeric reaction products of formaldehyde with urea, thiourea, biuret, or other homologs or derivatives thereof, such as N,N-ethyleneurea, N,N'-ethyleneurea, N,N'-dimethylurea, N,N'- diethylurea, N,N'-dimethoxymethylurea, N,N-dimethoxymethylurea, N,N'-diethoxyethylurea, tetrarnethoxyrnethylurea, tetraethoxyethylurea. Similar reaction products of formaldehyde with triazines, such as melamine may also be employed, such as N,N-dimethylmelamine and alcohol-modified melamineformaldehyde thermosetting resin condensates, e.g. of methyl and ethyl alcohols, for example, dimethoxymethylrnonomethylolmelamine. Preferably, the extent of condensation of these resin-forming aminoplast condensates is such that they are still soluble in water or self-dispersible therein to a colloidal condition.

The epoxy thermosetting resin-forming condensates may be either water-soluble or self-dispersible in water. The water-soluble types may be any of those having the Formulas I, II, III and IV:

1I=o-o11oH2o(oHroH(0H omonomoH-om p o o n) where x is a number having an average value of 1 to 3; H1OCHCH2O(CHshOCHzCH CH:

where y is a number having an average value of 2 to 4; and

o o (v) where is the p-phenylene group, and p is a munber having an average value of 1 to 3.

In the following examples which are illustrative of the invention, the parts and percentages are by weight unless otherwise specifically stated.

Example 1 One thousand parts of an aqueous dispersion containing 45% by weight of an emulsion copolymer of 86% of butyl acrylate, of vinyl acetate, and 4% of methacrylamide was prepared and 105 parts by weight of a 10% solution of sodium hydroxide was added. Then the dispersion was heated to a temperature of about 200 P. where it is maintained about 20 minutes ending up at a pH of 9.7. Approximately 50% of the vinyl acetate units were thus converted to vinyl alcohol units. Then the resulting sodium acetate is neutralized with dilute HCl to about pH 3. To 100 parts of the resulting copolymer dispersion containing 35 parts of the copolymer, there was added 0.5 part of oxalic acid. A carded Web of viscose rayon fibers, 2. denier, 1.5 inch length, weighing about 0.5 oz./sq. yd. was padded through the polymer dispersion to provide an 125% wet pickup. After air-drying, the treated web was heated at 260 F. for five minutes. The resulting bonded web was quite flexible and soft and withstood laundering in an auto matic washer employing cup of Tide in gallons of water at 140 F. The fabric also withstood dry-cleaning in a cleaning fluid formed of three gallons of carbon tetrachloride, one ounce of water, and 4.5 grams of the sodium salt of dicapryl sulfosuccinate. The dry-cleaning was effected in a portable agitator type of washer for a period of 30 minutes.

The bonded fabric was also bleached and scorched according to the AATCC test for damage caused by retained chlorine (69-1958). No discoloration of the fabric occurred as a result of this treatment.

Example 2 The procedure of Example 1 was repeated using an emulsion copolymer of 74% of butyl acrylate, of vinyl acetate, and 6% of methacrylamide, and hydrolyzing half of the vinyl acetate units so as to introduce 10% by weight of vinyl alcohol units. Good resistance was obtatined against both washing and dry-cleaning under the conditions specified in Example 1.

Example 3 (a) The procedure of Example 2 was repeated except the curing was effected at 300 F. for 5 minutes and the web was replaced with a 75/25 viscose rayon (3 denier, l-inch staple) bleached cotton (middling, inch) carded web weighing about 0.75 ounce/square yard. The wet pick-up was 600% on the weight of the fibers and in the final fabric the fiber to binder weight ratio was about 33:67.

(b) The procedure of part (a) was repeated except that the aqueous dispersion of the copolymer also contained 3.5% of dimethylol-N,N-ethyleneurea.

(1:) Part (a) was repeated except that the aqueous dispersion of the copolymer also contained 3 of dimethoxymethylurea.

(d) Part (a) was repeated except that the aqueous dispersion of the copolymer also contained 2.5% of trimethylolrnelamine.

(e) Part (a) was repeated except that the aqueous dispersion of the copolymer also contained 4% of a polyepoxide of the formula more resilient than that of part (a) and withstood a greater number of washing and dry-cleaning operations.

Example 4 The procedure of Example 2 is repeated on air-deposited webs of the following fibers:

(l) 100% regenerated cellulose (2.0'denier, 1.5 inch staple) 2 oz./sq. yd. carded web,

(2) 55% polyamide 66 nylon and 45% regenerated cellulose both 5 denier, 1.75 inch staple,

(3) 100% cotton (garnctted card waste, yarns) 4 oz./ sq. yd. carded web.

(4) 35% cotton and 65% poly(ethylene glycol terephthalate) 1.25 oz./sq. yd. carded web.

Example 5 Example 1 is repeated with similar results when the butyl acrylate in the copolymer is replaced with a corresponding proportion of Z-ethylhexyl acrylate or lauryl methacrylate.

It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims,

I claim:

1. As an article of manufacture, a soft non-woven fibrous product resistant to dry-cleaning and laundering in which the fibers are distributed in random array, fibers in the product being bonded together by a binder comprising a heat-cured product of a water-insoluble linear copolymer having units consisting essentially of about 4 to 6% by weight of units from methacrylamide, about 5 to 15 by weight of units of vinyl alcohol, about 1 to 45% by weight of vinyl acetate, and about 46 to by weight of an ester of the formula where n is an integer having a value of 1 to 2, and R is a (C -C )-alkyl group.

2. A product as defined in claim 1 in uct comprises cellulose fibers.

3. As an article of manufacture, a soft non-woven fibrous product resistant to dry-cleaning and laundering in which the fibers are distributed in random array, fibers in the product being bonded together by a binder comprising a heat-cured product of a water-insoluble linear copolymer having units consisting essentially of about 4 to 6% by weight of units from methacrylamide, about 8 to 10% by weight of units of vinyl alcohol, about 1 to 45 by weight of vinyl acetate, and about 46 to 90% by weight of an ester of the formula where n is an integer having a value of 1 to 2, and R is a (C C )-alkyl group.

4. A product as defined in claim 3 in comprises cellulose fibers.

5. As an article of manufacture, a soft non-woven fibrous product resistant to dry-cleaning and laundering in which the fibers are distributed in random array, fibers in the product being bonded together by a binder comprising a heat-cured product of 1) a water-insoluble linear copolymer having units consisting essentially of about 4 to 6% by weight of units from methacrylamide, about 5 to 15% by weight of units of vinyl alcohol, about 1 to 45 by weight of vinyl acetate, and about 46 to 90% by weight of an ester of the formula H2C=C (OH2)|11H 000R where n is an integer having a value of 1 to 2, and R is a roving and which the prodwhich the product C -C1a)-alky1 group, and (2) a water-dispersible thermo-' setting resin condensate selected from the group consisting of aminoplasts and polyepoxides, the proportion of (2) being up to 20% by weight of the copolymer.

6. A process of making a non-woven fabric which comprises associating in random array within a web or mat a mass of fibers, bringing into contact with the fibers a binder comprising an aqueous dispersion containing 5 to 60% by weight of a water-insoluble linear addition copolymer having units consisting essentially of about 4 to 6% by weight of units from methacrylamide, about 5 to 15% by weight of units of vinyl alcohol, about 1 to 7 45 by weight of vinyl acetate, and about 46 to 90% by weight of an ester of the formula where n is an integer having a value of 1 to 2, and R is a (C -C )-alkyl group, drying the fibrous mass containing the binder at a temperature above the T of the polymer to effect fusion of the polymer and bonding of the fibers thereby, and then heating the fibrous product at a temperature of 210 F. to 750 F. to render the bonded fibrous product resistant to laundering and dry-cleaning.

7. A process of making a non-woven fabric which comprises associating in random array within a web or mat a mass of fibers, bringing into contact with the fibers a binder comprising an aqueous dispersion containing 5 to 60% by weight of (1) a water-insoluble linear addition copolymer having units consisting essentially of about 4 to 6% by weight of units from methacrylamide, about 5 to 15% by weight of units of vinyl alcohol, about 1 to 45% by weight of vinyl acetate, and about 46 to 90% by weight of an ester of the formula where n is an integer having a value of 1 to 2, and R is a (C -C )-alkyl group, and (2) a water-dispersible thermosetting resin condensate selected from the group consisting of aminoplasts and polyepoxides, the proportion of (2) being up to 20% by weight of the copolymer, drying the fibrous mass containing the binder at a temperature above the T, of the polymer to effect fusion of the polymer and bonding of the fibers thereby, and then heating the fibrous product at a temperature of 210 F. to 750 F. to render the bonded fibrous product resistant to 1aundering and dry-cleaning.

References Cited in the file of this patent UNITED STATES PATENTS 2,545,702 Norris Mar. 20, 1951 2,681,866 Auchterlonie June 24, 1954 2,823,142 Sumner et a1. Feb. 11, 1958 2,923,653 Matlin et al. Feb. 2, 1960 2,931,749 Kine et a1 Apr. 5, 1960 FOREIGN PATENTS 549,946 Canada Dec. 10, 1957 

6. A PROCESS OF MAKING A NON-WOVEN FABRIC WHICH COMPRISES ASSOCIATING IN RANDOM ARRAY WITHIN A WEB OR MAT A MASS OF FIBERS, BRINGING INTO CONTACT WITH THE FIBERS A BINDER COMPRISING AN AQUEOUS DISPERSION CONTAINING 5 TO 60% BY WEIGHT OF A WATER-INSOLUBLE LINEAR ADDITION COPOLYMER HAVING UNITS CONSISTING ESSENTIALLY OF ABOUT 4 TO 6% BY WEIGHT OF UNITS FROM METHACRYLAMIDE, ABOUT 5 TO 15% BY WEIGHT OF UNITS OF VINYL ALCOHOL, ABOUT 1 TO 45% BY WEIGHT OF VINYL ACETATE, AND ABOUT 46 TO 90% BY WEIGHT OF AN ESTER OF THE FORMULA 